Unlike Verizon's other LTE handsets, iPhone 5 will drop data to make calls.

Share this story

Early reports and tweets from Verizon Wireless support staff suggested that simultaneous data usage and voice calls would be possible on the new LTE-equipped iPhone 5. A new statement says that's not in fact the case: taking a call on the iPhone 5 will cause the handset to drop any data connection.

The support person tweeted yesterday that "You can run voice/data at the same time on 4G devices, while in a 4G area!" when asked if the 4G iPhone 5 would permit simultaneous voice and data. Today, however, AllThingsD noted there was no simultaneous voice and data after all. We asked Verizon and were told "iPhone 5 was designed to allow simultaneous voice calling on the Verizon Wireless network while browsing the Internet over WiFi. This is no different from the current iPhone 4S. For further details, check with Apple."

A long-standing feature of the CDMA networks used by Verizon and Sprint is they don't permit simultaneous use of a data connection and a voice connection. Due to their use of the data-only EVDO standard (instead of the data plus voice EVDV alternative), any inbound or outbound call forces the phone to drop the data connection and revert to a CDMA connection.

In some regards, LTE is no different. Voice over LTE (VoLTE) is coming, eventually (the first commercial rollout started last month in South Korea and MetroPCS in parts of the US), but as of right now, there's no way to route a voice call over LTE on either Verizon or Sprint. However, all of Verizon's other 4G phones can connect to the CDMA network, for calls, and the LTE network, for data, simultaneously. This allows concurrent usage of voice and data, albeit over two separate network connections with two separate antennas. Some of them can do a similar trick with EVDO and CDMA, using two antennas to connect to both networks concurrently (a feature called SVDO).

iPhone 5, however, lacks this ability to connect to the legacy voice network and LTE network simultaneously, forcing the choice: data or voice, but not both.

This could explain the Verizon rep's error; every LTE handset currently available on the network can use voice and data, and he assumed that the forthcoming iPhone 5 was no exception.

The inability to use LTE with any other cellular connection also strikes AT&T's handsets, but is much less significant there: on AT&T, the iPhone 5 can fall back to HSPA+, and HSPA+ does support simultaneous voice and data. You won't get full LTE speeds when on a voice call, but you'll still be able to make searches, get directions, check for e-mails, and anything else that requires a data connection.

As for why the iPhone 5 doesn't support simultaneous CDMA and LTE connections (in contrast to competing Android products), we've reached out to Apple for details. At the time of writing, we are awaiting a response. In lieu of an official answer, we would speculate that it is a limitation of iPhone 5's "dynamic antenna," and that can't be tuned simultaneously to all the frequencies it would need to support simultaneous CDMA and LTE connectivity (other handsets include multiple antennas to support multiple cellular connections).

Update: The New York Times is reporting the same theory; the iPhone 5 would need an additional antenna to allow connection to CDMA and LTE networks simultaneously.

Odd decisions to be making on just iPhones. My Verizon Galaxy S3 has no trouble with data connection multitasking while I'm mid-call. I just yesterday morning pulled out of a call to go to Google Maps and find my Dad a restaurant local to him, then pulled up the website and got him the phone number. Technically that's three data connections (2G/3G for the phone call, GPS for Maps, and 4G for Chrome).

I think it should just downgrade to HSPA+ and allow the call to continue. I'm not sure what the hand-off is like between those two.

From elsewhere, it reads like you lose all data because of the single dynamic antenna. It sounds a bit dumb, to say the least, so I would figure this is the better explanation since the alternative kills functionality in the satnav-while-taking-a-call scenario.

Odd decisions to be making on just iPhones. My Verizon Galaxy S3 has no trouble with data connection multitasking while I'm mid-call. I just yesterday morning pulled out of a call to go to Google Maps and find my Dad a restaurant local to him, then pulled up the website and got him the phone number. Technically that's three data connections (2G/3G for the phone call, GPS for Maps, and 4G for Chrome).

How does GPS count? You could argue the magnetometer and gyroscope are "data connections" then too. It's hardly the same as a radio transceiver as with the 2 to 4G ones.

if you ran Skype on an LTE phone could you simultaneously run a 2nd data channel or can't they do that either? My desktop can do that over regular tcp/ip why should not a mobile phone be able to do it?

Odd decisions to be making on just iPhones. My Verizon Galaxy S3 has no trouble with data connection multitasking while I'm mid-call. I just yesterday morning pulled out of a call to go to Google Maps and find my Dad a restaurant local to him, then pulled up the website and got him the phone number. Technically that's three data connections (2G/3G for the phone call, GPS for Maps, and 4G for Chrome).

Technically, it's 2 data connections. GPS is not a connection, just a reciever.

I switched from AT&T because they were pissing me off, and Verizon had better customer service reviews for the last few years. I should have stuck with AT&T and kept my grandfathered data _there_; Verizon takes months to release updates for the Galaxy Nexus, the ROM teams get everything updated and stable within a week.

This is my hypothesis about AT&T. But Verizon and Sprint can't downgrade to HSPA because they have no HSPA networks to downgrade to.

Hoo boy. That's a pretty glaring fault there, then. Better hope no one wants to use their smartphone to actually do phone things simultaneously with looking stuff up on teh intartubez. It does remind me of how much more limited my own network can be for things like 2G because Three tended to mainly sell themselves as a forward thinking 3G network, and only borrowed some 2G spectrum off Orange for when their users were out of reach of one of their towers. A bigger issue years ago when 3G was still new and limited in coverage, now, not so much.

Nice... And now all the At&t users that just said they were moving to VZW or Sprint, because the At&t was not a real "world" LTE, will once again buy an At&t phone... Not being able to handle voice and data is a real PITA...

As an iPhone 4 owner on Verizon, this really pisses me off. I had been absolutely counting on this simultaneous data/voice capability in the next gen iPhone, because I tether and have a lot of employees who tether on iPhones as well. Every time a call comes in, data drops and you can't do anything but re-establish after the call is over. Not to mention, have a fair amount of money invested in an app ecosystem I'm not sure I'll continue to support; this could be a deal breaker for me on the iPhone 5.

Due to their use of the data-only EVDO standard (instead of the data plus voice EVDV alternative)

IIRC, CDMA2000 1xEV-DV was canceled many, many years ago. (I'd guess 8 to 9 years ago). It was going to support higher speed data (IIRC around 8Mbps data rate) and voice at the same time. Instead, Qualcomm canceled that project, and put all of their resources into EV-DO Rev A (and later Rev B).

A couple of years ago, the CDMA Development Group (CDG) came out with a standard known as SVDO, which allows a 3G CDMA phone to connect to both a voice and data network at the same time. Many CDMA chipsets support that standard (such as the HTC Thunderbolt), however, IIRC, it relies on two antennas.

So on ATT, if I have a connection open with Prompt or another terminal emulator, calls could go to voicemail if I'm using LTE?

I think it should just downgrade to HSPA+ and allow the call to continue. I'm not sure what the hand-off is like between those two.

The handoff should work. What happens if you're sitting in a taxi and drop out of LTE range while on a call? My guess is it only takes a millisecond or so to jump from one network to another, and there will be no data/voice dropout (both have buffers and algorithms to handle small amounts of packet loss).

Due to their use of the data-only EVDO standard (instead of the data plus voice EVDV alternative)

IIRC, CDMA2000 1xEV-DV was canceled many, many years ago. (I'd guess 8 to 9 years ago). It was going to support higher speed data (IIRC around 8Mbps data rate) and voice at the same time. Instead, Qualcomm canceled that project, and put all of their resources into EV-DO Rev A (and later Rev B).

A couple of years ago, the CDMA Development Group (CDG) came out with a standard known as SVDO, which allows a 3G CDMA phone to connect to both a voice and data network at the same time. Many CDMA chipsets support that standard (such as the HTC Thunderbolt), however, IIRC, it relies on two antennas.

One of the reasons that EVDV was cancelled, AIUI, was that Qualcomm stopped bothering because Sprint and Verizon both plumped for EVDO.